#define _CRT_SECURE_NO_WARNINGS 1

#include<stdio.h>

int he(int x)
{
	double sum = 0;
	double a = 1;
	double b = 1;
	for (int i = 1; i <= x; i++) {
		if (i == 1) {
			a = 1;
			b = 1;
		}
		else {
			a *= i - 1;
			b *= (2 * (i - 1) + 1);

		}
		sum += a / b;
	}
	//printf("%lf\n", b);
	//printf("%lf\n", a);

	printf("%.10lf", sum);
	return 1;
}
int main()
{
	int n;
	scanf("%d", &n);
	he(n + 1);
	return 0;
}